The present invention relates to an improved electric mass and force measuring apparatus of the type including a first force transducer for providing an electrical output signal proportional to the gravitational force of the mass to be determined, a second force transducer for providing an electrical output signal proportional to the gravitational force of a known mass, and signal processing means for calculating and indicating the measure of the unknown mass.
When measuring physical quantities, for example forces, it has long been known to use measuring devices which convert the physical quantity to an electric signal. The signal is then processed in any appropriate way so that the measurement test result can be registered or visually displayed in processing means. In weighing equipment, force transducers, load cells or similar transducers are often used as measuring devices in order to achieve an analog voltage or signal proportional to the gravitational force of the unknown mass. The analog signal is amplified and fed to an analog-to-digital converter for producing a digital output signal corresponding to the mass of the load.
It is often difficult to attain acceptable accuracy in weighing equipments of the above-mentioned type, especially when weighing on ships. In order to achieve a true measuring result, it is necessary that the measuring direction of the force transducer coincide with the vertical. When measuring on a firm support, it is certainly possible to compensate for tilting, but on ships equipped with means for weighing articles at sea, it has not been possible on account of the movement of the ship when the sea is high. As a result, in some circumstances, it has been necessary to accept an error of as much as 10 percent of the measuring result.
It is not only the variations of a tilting support that has a negative effect on the measuring result when weighing at sea. Also variations of the vertical acceleration due to movement of the ship up and down vertically, for instance when pitching, result in a misleading measuring result.